FreeRTOS/Demo/Common/Minimal/death.c

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*/

/**
 * Create a single persistent task which periodically dynamically creates another
 * two tasks.  The original task is called the creator task, the two tasks it
 * creates are called suicidal tasks.
 *
 * One of the created suicidal tasks kill one other suicidal task before killing
 * itself - leaving just the original task remaining.
 *
 * The creator task must be spawned after all of the other demo application tasks
 * as it keeps a check on the number of tasks under the scheduler control.  The
 * number of tasks it expects to see running should never be greater than the
 * number of tasks that were in existence when the creator task was spawned, plus
 * one set of four suicidal tasks.  If this number is exceeded an error is flagged.
 *
 * \page DeathC death.c
 * \ingroup DemoFiles
 * <HR>
 */


#include <stdlib.h>

/* Scheduler include files. */
#include "FreeRTOS.h"
#include "task.h"

/* Demo program include files. */
#include "death.h"

#define deathSTACK_SIZE		( configMINIMAL_STACK_SIZE + 60 )

/* The task originally created which is responsible for periodically dynamically
creating another four tasks. */
static portTASK_FUNCTION_PROTO( vCreateTasks, pvParameters );

/* The task function of the dynamically created tasks. */
static portTASK_FUNCTION_PROTO( vSuicidalTask, pvParameters );

/* A variable which is incremented every time the dynamic tasks are created.  This
is used to check that the task is still running. */
static volatile uint16_t usCreationCount = 0;

/* Used to store the number of tasks that were originally running so the creator
task can tell if any of the suicidal tasks have failed to die.
*/
static volatile UBaseType_t uxTasksRunningAtStart = 0;

/* Tasks are deleted by the idle task.  Under heavy load the idle task might
not get much processing time, so it would be legitimate for several tasks to
remain undeleted for a short period. */
static const UBaseType_t uxMaxNumberOfExtraTasksRunning = 3;

/* Used to store a handle to the task that should be killed by a suicidal task,
before it kills itself. */
TaskHandle_t xCreatedTask;

/*-----------------------------------------------------------*/

void vCreateSuicidalTasks( UBaseType_t uxPriority )
{
UBaseType_t *puxPriority;

	/* Create the Creator tasks - passing in as a parameter the priority at which
	the suicidal tasks should be created. */
	puxPriority = ( UBaseType_t * ) pvPortMalloc( sizeof( UBaseType_t ) );
	*puxPriority = uxPriority;

	xTaskCreate( vCreateTasks, "CREATOR", deathSTACK_SIZE, ( void * ) puxPriority, uxPriority, NULL );

	/* Record the number of tasks that are running now so we know if any of the
	suicidal tasks have failed to be killed. */
	uxTasksRunningAtStart = ( UBaseType_t ) uxTaskGetNumberOfTasks();
	
	/* FreeRTOS.org versions before V3.0 started the idle-task as the very
	first task. The idle task was then already included in uxTasksRunningAtStart.
	From FreeRTOS V3.0 on, the idle task is started when the scheduler is
	started. Therefore the idle task is not yet accounted for. We correct
	this by increasing uxTasksRunningAtStart by 1. */
	uxTasksRunningAtStart++;
	
	/* From FreeRTOS version 7.0.0 can optionally create a timer service task.  
	If this is done, then uxTasksRunningAtStart needs incrementing again as that
	too is created when the scheduler is started. */
	#if configUSE_TIMERS == 1
		uxTasksRunningAtStart++;
	#endif
}
/*-----------------------------------------------------------*/
					
static portTASK_FUNCTION( vSuicidalTask, pvParameters )
{
volatile long l1, l2;
TaskHandle_t xTaskToKill;
const TickType_t xDelay = ( TickType_t ) 200 / portTICK_PERIOD_MS;

	if( pvParameters != NULL )
	{
		/* This task is periodically created four times.  Two created tasks are
		passed a handle to the other task so it can kill it before killing itself.
		The other task is passed in null. */
		xTaskToKill = *( TaskHandle_t* )pvParameters;
	}
	else
	{
		xTaskToKill = NULL;
	}

	for( ;; )
	{
		/* Do something random just to use some stack and registers. */
		l1 = 2;
		l2 = 89;
		l2 *= l1;
		vTaskDelay( xDelay );

		if( xTaskToKill != NULL )
		{
			/* Make sure the other task has a go before we delete it. */
			vTaskDelay( ( TickType_t ) 0 );

			/* Kill the other task that was created by vCreateTasks(). */
			vTaskDelete( xTaskToKill );

			/* Kill ourselves. */
			vTaskDelete( NULL );
		}
	}
}/*lint !e818 !e550 Function prototype must be as per standard for task functions. */
/*-----------------------------------------------------------*/

static portTASK_FUNCTION( vCreateTasks, pvParameters )
{
const TickType_t xDelay = ( TickType_t ) 1000 / portTICK_PERIOD_MS;
UBaseType_t uxPriority;

	uxPriority = *( UBaseType_t * ) pvParameters;
	vPortFree( pvParameters );

	for( ;; )
	{
		/* Just loop round, delaying then creating the four suicidal tasks. */
		vTaskDelay( xDelay );

		xCreatedTask = NULL;

		xTaskCreate( vSuicidalTask, "SUICID1", configMINIMAL_STACK_SIZE, NULL, uxPriority, &xCreatedTask );
		xTaskCreate( vSuicidalTask, "SUICID2", configMINIMAL_STACK_SIZE, &xCreatedTask, uxPriority, NULL );

		++usCreationCount;
	}
}
/*-----------------------------------------------------------*/

/* This is called to check that the creator task is still running and that there
are not any more than four extra tasks. */
BaseType_t xIsCreateTaskStillRunning( void )
{
static uint16_t usLastCreationCount = 0xfff;
BaseType_t xReturn = pdTRUE;
static UBaseType_t uxTasksRunningNow;

	if( usLastCreationCount == usCreationCount )
	{
		xReturn = pdFALSE;
	}
	else
	{
		usLastCreationCount = usCreationCount;
	}
	
	uxTasksRunningNow = ( UBaseType_t ) uxTaskGetNumberOfTasks();

	if( uxTasksRunningNow < uxTasksRunningAtStart )
	{
		xReturn = pdFALSE;
	}
	else if( ( uxTasksRunningNow - uxTasksRunningAtStart ) > uxMaxNumberOfExtraTasksRunning )
	{
		xReturn = pdFALSE;
	}
	else
	{
		/* Everything is okay. */
	}

	return xReturn;
}